Carpet plug cutter

ABSTRACT

A tool for cutting circular plugs of carpeting solely by rotary cutting action and without the use of impact forces is disclosed. Cutter blade assemblies for use in such tool providing serrated cutting edges with various types of serrations are described. Means for quickly and easily interchanging cutter blade assemblies of various diameters in the tool are disclosed.

United States Patent 1191 Acheson Jan. 22, 1974 CARPET PLUG CUTTER3,111,995 11/1963 Dahl 30/310 I ento Me vin G- Acheson4555 Auburn3,171,200 3/1965 Poppenga 30/130 Ave., Suite A, Sacramento, Calif. 95841Primary Examiner-James L. Jones, Jr. Assistant Examiner-J. C. Peters[22] F1led: Oct. 19, 1972 [21] Appl. No.: 298,839 57] ABSTRACT [52] Us.CL 30/124 30/310 A tool for cutting circular plugs of carpeting solelyby [51] Int Cl. B26b 3/08 rotary cutting action and without the use ofimpact [58] Field 286 310 forces is disclosed. Cutter blade assembliesfor use in 6 such tool providing serrated cutting edges with varioustypes of serrations are described. Means for quickly [56] ReferencesCited and easily interchanging cutter blade assemblies of UNITED STATESPATENTS various diameters in the tool are disclosed. 3,053,203 9/1962Gaddini 30/130 X 10 Claims, 4 Drawing Figures PATENIEB JAN 2 2 I974 FIG3 CARPET PLUG CUTTER BACKGROUND OF THE INVENTION This invention relatesto a tool for cutting circular.

plugs from installed carpeting, without otherwise disturbing thecarpeting; in order to provide access through the carpeting or to removestained or burned sections from the carpeting for subsequent replacementby circular plugs cut from undamaged carpeting and more particularly tosuch a tool designed for rotary cutting action without the use of impactforces.

Carpet repair tools for cutting circular plugs from installed carpeting,comprising a circular blade adapted to be driven through the carpetingby impact, have been proposed heretofore. However, such tools have anumber of disadvantages in use, the most severe of which is that thecarpet must be cut by a single impact on the tool, if possible. It willbe understood that an impact applied to the tool will tend to cause itto bounce away from the carpet after the impact thereon. Thus, if thecarpet is not cut'cleanly by the tool upon first impact it will benecessary to return the tool to exactly the same position for second andsubsequent impacts. This is difficult to do because the location of theinitial partial cut will tend to be hidden by the nap or pile of thecarpet. Even if the tool is manually held against the carpet whenimpacted, the tool will tend to move slightly after each impactresulting in ragged and uneven cutting by the circular blade about itsperiphery including possible damage to the adjacent nap or pile of thecarpet.

On the other hand, if the initial impact is greater than necessary tocut the carpet cleanly about the entire periphery of the blade of thetool, it may damage the underlying pad or even the floor beneath the padin addition to the carpet itself. Various schemes have been proposed tolimit the travel of the blade upon impact to no more than necessary tocut through the carpet, as shown for example in U.S. Pat. No. 3,171,200.However, all of such schemes necessarily transfer some part of theimpact force to another member of the tool thus either tending to makeit more difficult to secure a clean circular cut if the impact ismarginally low or tending to compress or dent the underlying pad andflooring if the impact is too great. It will be understood that theblade of such prior art tools must be kept uniformly sharp about itsentire periphery in order to avoid ragged cutting action and minimizethe required impact.

It is an object of this invention to provide a tool for cutting circularplugs from carpeting without the use of impact forces.

It is a further object of this invention to provide a tool for cuttingcircular plugs from carpeting in which the likelihood of the tool makinga ragged or uneven cut is reduced.

It is another object of this invention to provide a tool for cuttingcircular plugs from carpeting in which the importance of uniformsharpness of the blade is reduced.

It is yet another object of this invention to provide a tool for cuttingcircular plugs from carpeting which may be used to cut plugs of varioussizes with greater ease, accuracy, and safety and with less maintenancethan similar tools of the prior art.

SUMMARY OF THE INVENTION The carpet plug cutter of this inventioncomprises a hollow tubular housing one end of which is open andterminates in a plane perpendicular to the axis of the housing. Aplurality of carpet engaging pins are mounted at such one end of thehousing and extend therefrom along the axis of the housing. An elongateddrive rod having one end within the housing and the other end projectingfrom the other end of the housing is mounted at such other end of thehousing for reciprocal movement of its axis of elongation along the axisof the housing and for rotation about its axis of elongation. The end ofthe drive rod within the housing is adapted to removably receive acutter blade assembly and the other end of the drive rod is providedwith knob means having a dimension transverse to the axis of the housingwhich is at least equal to the radius of the housing. A spring means isprovided between the housing and the drive rod to bias the drive rodinto its position of maximum spacing between the housing and the knobmeans. The cutter blade assembly includes a hollow cylindrical blademember having one end provided with a serrated and beveled knife edge.The blade member is removably mounted at its other end on the end of thedrive rod within the housing and coaxially with the axis of elongationof the drive rod. In use a cutter blade assembly of the desired diameteris mounted on the end of the drive rod and the open end of the housingis placed against the carpet. The drive rod is manually forced into thehousing, against the force of the spring, and rotated about its axis ofelongation to bring the serrated knife edge into cutting engagement withthe carpet. The carpet gripping pins insure that the tool is held inplace and that the housing is held against rotation during operation.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top view of a toolaccording to a preferred embodiment of this invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 showinga cutter blade according to one embodiment of this invention.

FIG. 3 is a top view of a cutter blade assembly suitable for use in atool according to another embodiment of this invention.

FIG. 4 is a side view in elevation of a cutter blade assembly for use ina tool according to a further embodiment of this invention.

DETAILED DECRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2a tool according to a preferred embodiment of this invention is shown.The tool comprises a hollow tubular housing 10 which may be a hollowmetal cylinder for example. Carpet gripping means are provided at oneend 11 of the housing 10 and in the embodiment shown such means comprisea plurality of elongated sharpened pins 12 spaced about the periphery ofthe housing 10 and extending along the axis thereof.

The other end 13 of the tubular housing 10 is provided with anappropriate means such as the strut and guide structure 14 shown inFIGS. 1 and 2 for rotably supporting an elongated cylindrical drive rod16 with its axis of elongation along the axis of the housing 10 and withone end 15 within the housing 10 and the other end 17 projectingtherefrom. The projecting end 17 of the drive rod 16 is provided with aportion extending transversely of the axis of elongation thereof bymeans of a knob 18 affixed thereto. The transverse dimensions of suchknob 18 must be at least equal to the radius of the tubular housing forreasons which will be discussed hereinafter.

A compression spring 19 is received about the drive rod 16 with one endof such spring 19 hearing on the knob 18 and the other end of the springbearing on the facing surface of the strut and guide structure 14 inorder to urge the drive rod 16 toward maximum projection of the end 17thereof from the housing 10. It will be understood that the end of thedrive rod 16 within the housing 10 is provided with an appropriate stopmeans or enlargement to prevent it from passing through the strut andguide structure 14 under the influence of the spring 19. The force ofthe spring 19 should be sufficient to maintain the drive rod 16 in theposition relative to the housing 10 shown in FIG. 2 when the tool is notin use regardless of the orientation of the tool. Otherwise, the forceexerted by the spring 19 is not critical except that it will tend tooppose the movement of the drive rod 16 with respect to the housing 10when the tool is in use and should therefore be kept as small aspractical. Similarly, the abutment between the spring 19 and the knob 18will tend to introduce friction when the knob 18 is rotated to rotatethe drive rod 16 with respect to housing 10 in use. Thus, an appropriatebushing or other means of reducing friction may be interposed betweenthe end of the spring 16 and the knob 18 as necessary or desirable.

A cutter blade assembly 20 is removably mounted on the end 15 of thedrive rod 16 within the housing 10. The cutter blade assembly comprisesa hollow cylindrical blade member 22 having one end 21 beveled andserrated to form a cutting edge and the other end 23 mounted on a rigidplate 24. The plate 24 is provided with a portion 25 of a socket wrenchtype coupling means for engagement with a mating portion 26 provided onthe end 15 of the drive rod 16. As shown in FIG. 2 the male portion 25of the socket wrench type coupling means is provided on the plate 24 andthe female portion 26 in the end 15 of the drive rod 16, however, itwill be understood that this arrangement could be reversed as shown inFIG. 3. It will also be understood that it is contemplated that a numberof cutter blade assemblies similar in structure to the assembly 20 buteach having a cylindrical cutting blade 22 of different diameter fromthe others will be used interchangeably in the tool to cut circularcarpet plugs of different diameters as necessary or desirable.

Referring to FIG. 3 a top view of a cutter blade assembly 20 which maybe made in a series of diameters suitable for use in a tool according tothis invention is shown. As shown in FIG. 3 a socket wrench typecoupling may be provided by a square socket 25'in the plate 24 adaptedto receive a square shank 26 provided on the end 15 of the drive rod 16,for example. The plate 24 may be provided with apertures 28 in order toreduce the mass of the assembly and to enable the cutting operation tobe observed while it is in progress.

Referring to FIG. 4 it will be seen that the cylindrical blade 22 may beconveniently made by sharpening and serrating one edge of an elongatedflat strip of steel which is then wrapped around the periphery of theplate 24 at its other edge and the ends thereof fastened to the plate bymeans of screws 29, for example. The length of the strip is selected inrelation to the diameter of the plate 24 so that the ends of the stripwill abut each other to form a non-overlapping seam 30 when the assemblyis completed. Thus, the blade 22 may be easily removed and flattened tofacilitate resharpening of the cutting edge thereof as necessary. It hasbeen found that a bevel of about 5 on the cutting edge 21, 21' of theblade 22 provides efficient cutting action in the tool of thisinvention.

It will be noted that the serrations in the cutting edge 21 of the blade22 shown in FIG. 4 are difi'erent from the serrations in the cuttingedge 21 of the blade shown in FIG. 2. In both cases the serrations aremade of alternately concave and convex arcuate surfaces and suchserrations are an essential feature of this invention in order to enablemanual rotary cutting action. It has been found that serrations of avariety of arcuate shapes may be used but they are subject to certainimportant limitations.

If no serrations at all are provided in the cutting edge, it issubstantially impossible to manually perform any rotary cutting actionsince a great deal of downward pressure and a very large number ofrotation of the blade would be required even in cutting a carpet plug ofsmall diameter, thus exhausting the operator. According to thisinvention serrations are provided which enable a proper balancingbetween the downward pressure, the number of rotations, and the rotaryforce required to cut a plug from an average carpet without exhaustingthe physical capabilities of the average manual operator. If a largenumber of small serrations are used they will either require a largeamount of downward force, as in the case of no serrations at all, orthey will require a large amount of rotational force depending on theangle at which the surface of the serrations engage the carpet.According to one aspect of this invention, it has been found thatserrations formed of arcuate surfaces will tend to provide a balancebetween the required downward force and the required rotational forcewhich would be practical for manual operation. However, according toanother aspect of this invention it has been found that the use of alarge number of small serrations would tend to require a large number ofrotations of the blade to cut through the carpet which would beexhausting and time consuming for the average manual operator.

According to the teaching of this invention carpet plugs up to adiameter of about 3 inches are practical to cut manually by rotarycutting action if the serrations are formed of alternately concave andconvex arcuate surfaces. Tests indicate that the number of serrationsspaced about the cutting blade should be at least five and not more thanabout twenty. Although it is believed that a wavy edge blade in whichall of the arcuate surfaces have the same curvature, as shown in FIG. 2,is preferable in terms of avoiding operator fatigue it has been foundthat a scalloped edge" blade in which the convex arcuate surfaces havegreater curvature than the concave surfaces, as shown in FIG. 4, is alsopractical for use in manually cutting carpet plugs up to about threeinches in diameter accordng to this invention. It is believed that theradius of curvature of the arcuate surfaces forming the serrations mustbe between 0.05 inch and 0.05 inch in order to provide efficient cuttingaction.

In order to provide sufficient leverage to enable the average operatorto manually cut the average carpet with a tool according to thisinvention, it is necessary that the end 17 of drive rod 16 have atransverse dimension, such as is provided by knob 18, at least equal tothe radius of the housing 10. It will be understood that the diameter ofthe housing of the tool determines the maximum diameter of the cutterblade assembly 20 that can be used therein since the cutter bladeassembly is received in such housing. This arrangement protects thecutting edge 21, 21' from damage when the tool is not in use and tendsto prevent any accidental cutting, including injury to the operator, bythe cutting edge 21, 21. The socket wrench type coupling between cutterblade assemblies 20 and the drive rod 16 enables assemblies 20 withvarious diameters of cutting blades 22 to be used interchangeably in thetool and the structure of the cutter blade assemblies 20 provides forease in removal of the blades 22 for efficient resharpening thereof intheir flattened or strip condition. In addition, the resharpening ofserrations formed of arcuate surfaces according to this invention hasbeen found to be most satisfactory and efficient as compared to theresharpening of serrations formed of rectilinear surfaces, for example.Furthermore, it has been found that maintenance requirements, includingresharpening of the blade 22, forthe tool according to this inventionare far less stringent than for similar devices of the prior art.

What is claimed is:

l. A tool for cutting circular plugs of carpeting comprising:

a. a hollow tubular housing having an open end terminating in a planeperpendicular to the axis of the housing;

b. carpet gripping means about the periphery of said open end of saidhousing;

c. an elongated drive rod mounted on the other end of said housing, oneend of said drive rod being within said housing and the other end ofsaid drive rod projecting from said other end of said housing, saiddrive rod being mounted for reciprocal movement of the axis ofelongation thereof along the tubular axis of said housing and forrotation about said axis of elongation, said other end of said drive rodbeing provided with a portion extending transversely of the axis ofelongation thereof for a distance at least equal to the radius of saidtubular housing;

(1. spring means urging said other end of said drive rod to project fromsaid housing, and

e. a cutter blade assembly comprising a hollow cylindrical blade ofsmaller diameter than said housing, a beveled cutting edge with arcuateconvex serrations formed therein at one end of said blade and meansremovably mounting the other end of said blade on said one end of saiddrive rod within said housing coaxially with said axis of elongation ofsaid drive rod.

2. A tool as claimed in claim 1 wherein said carpet gripping meanscomprise a plurality of elongated sharp pins spaced about the peripheryof said open end of said housing and extending therefrom in a directionsubstantially parallel to the axis of said housing.

3. A tool as claimed in claim 1 wherein said dimension of said other endof said drive rod transverse to the axis of elongation thereof isprovided by a knob having transverse dimensions greater than the radiusof said tubular housing.

4. A tool as claimed in claim 1 wherein said means removably mountingsaid other end of said cylindrical blade on said one end of said driverod within said housing comprises a socket wrench type couplingtherebetween.

5. A tool as claimed in claim 4 wherein said cylindrical blade is formedby bending a flat strip into a circle with the ends of said strip inabutment and said means removably mounting said blade on said drive rodincludes a rigid plate member with a circular periphery to which saidblade is attached.

6. A tool as claimed in claim 1 wherein said serrations of said serratedcutting edge are formed by alternately concave and convex arcuatesurfaces.

7. A tool as claimed in claim 6 wherein said concave and convex arcuatesurfaces have substantially the same curvature.

8. A tool as claimed in claim 6 wherein said concave arcuate surfaceshave a curvature less than the curvature of said convex arcuatesurfaces.

9. A tool as claimed in claim 6 wherein said serrations include at leastabout five and not more than about twenty convex arcuate surfaces.

10. A tool as claimed in claim 9 wherein said concave and convex arcuatesurfaces have a radius of curvature between 0.05 inch and 0.05 inch.

1. A tool for cutting circular plugs of carpeting comprising: a. ahollow tubular housing having an open end terminating in a planeperpendicular to thE axis of the housing; b. carpet gripping means aboutthe periphery of said open end of said housing; c. an elongated driverod mounted on the other end of said housing, one end of said drive rodbeing within said housing and the other end of said drive rod projectingfrom said other end of said housing, said drive rod being mounted forreciprocal movement of the axis of elongation thereof along the tubularaxis of said housing and for rotation about said axis of elongation,said other end of said drive rod being provided with a portion extendingtransversely of the axis of elongation thereof for a distance at leastequal to the radius of said tubular housing; d. spring means urging saidother end of said drive rod to project from said housing, and e. acutter blade assembly comprising a hollow cylindrical blade of smallerdiameter than said housing, a beveled cutting edge with arcuate convexserrations formed therein at one end of said blade and means removablymounting the other end of said blade on said one end of said drive rodwithin said housing coaxially with said axis of elongation of said driverod.
 2. A tool as claimed in claim 1 wherein said carpet gripping meanscomprise a plurality of elongated sharp pins spaced about the peripheryof said open end of said housing and extending therefrom in a directionsubstantially parallel to the axis of said housing.
 3. A tool as claimedin claim 1 wherein said dimension of said other end of said drive rodtransverse to the axis of elongation thereof is provided by a knobhaving transverse dimensions greater than the radius of said tubularhousing.
 4. A tool as claimed in claim 1 wherein said means removablymounting said other end of said cylindrical blade on said one end ofsaid drive rod within said housing comprises a socket wrench typecoupling therebetween.
 5. A tool as claimed in claim 4 wherein saidcylindrical blade is formed by bending a flat strip into a circle withthe ends of said strip in abutment and said means removably mountingsaid blade on said drive rod includes a rigid plate member with acircular periphery to which said blade is attached.
 6. A tool as claimedin claim 1 wherein said serrations of said serrated cutting edge areformed by alternately concave and convex arcuate surfaces.
 7. A tool asclaimed in claim 6 wherein said concave and convex arcuate surfaces havesubstantially the same curvature.
 8. A tool as claimed in claim 6wherein said concave arcuate surfaces have a curvature less than thecurvature of said convex arcuate surfaces.
 9. A tool as claimed in claim6 wherein said serrations include at least about five and not more thanabout twenty convex arcuate surfaces.
 10. A tool as claimed in claim 9wherein said concave and convex arcuate surfaces have a radius ofcurvature between 0.05 inch and 0.05 inch.